1. Field of the Invention
The present invention relates to a remaining gas amount calculating device for determining the amount of gas remaining in a gas container holding a specified gas.
2. Description of the Related Art
Conventionally, there are devices that gradually let out and use gas held in a gas container holding a specified gas. Such devices include, for example, vehicles that run utilizing electric power generated with a fuel cell system including fuel cells. Such a fuel cell system is provided with a hydrogen tank holding hydrogen gas. The fuel cell generates electric power by causing a reaction between hydrogen gas supplied from the hydrogen tank and oxygen in the air. Such a fuel cell system is also generally provided with a measuring device for measuring the remaining amount in the hydrogen tank (see JP-A 2005-240854, for example).
This fuel cell system includes a fuel cell, a compressor for supplying air to the fuel cell, a hydrogen tank connected through a decompression valve to the fuel cell to provide hydrogen gas to the fuel cell, a pressure sensor for measuring the pressure in the hydrogen tank, a temperature sensor for measuring the temperature in the hydrogen tank, and a controller. The fuel cell generates electric power by causing a reaction between hydrogen gas depressurized to a specified pressure with the decompression valve and oxygen gas in the air supplied from the compressor. The controller, according to the values detected by the pressure sensor and the temperature sensor, calculates the remaining amount of hydrogen gas in the hydrogen tank both as a display value for a pressure meter and as a display value for a mass meter. When the pressure measurement is equal to or more than a specified value, a display value for the mass meter is displayed on the fuel meter; and when the pressure measurement is less than the specified value, a display value for the pressure meter is displayed on the fuel meter.
However, as the above-described conventional fuel system uses a pressure sensor that directly measures the pressure in the hydrogen tank, it has been necessary to use a pressure sensor that has a sealing property against high pressure gas, and is accordingly expensive. Moreover, it has also been necessary to make the structure around the pressure sensor elaborate and sturdy.